Method of treating steel armor-plates, &amp;c.



UNITED STATES PATENT QFFIOE.

ROBERT A. HADFIELD, SHEFFIELD, ENGLAND.

METHOD O TREATING STEEL ARMOR-PLATES, 81.0. v

, Specification of Letters Patent. 4

Patented Qct. 17, 1905.

Application filed Jim 28,1905. Serial No. 207,344.

the following description is a specification.

This invention has reference to an improved manufacture or treatment of steel for the purpose of increasing the toughness thereof. and is specially applicable to the treatment of nickel chromium steel, whether containing tungsten or not, such as is described in the specification of British Letters Patent granted to me, No. 16,132 of 1901. r The invention may be advantageously applied to the treatment of armor-plates and other articles of steel in the form of castings.

According to one method of carrying out my invention the article-for example, a cast armor-plate of steel of the kind referred to is heated uniformly to a temperature of from about 950 0. (nine hundred'and fifty degrees centigrade) to about 1, l00 O. (eleven hundred degrees centigrade) and then cooled, preferably in air, which avoids sudden cooling such as would result if the article were quenched in a hardening liquid. It is then reheated to a temperature of about 700 (1. (seven hundred degrees centigrade) and cooled slowly, preferably in, the furnacein which the heating was previously effected, after which it is again-heated to a temperature of about 700 (J. (seven hundred degrees centigrade) and allowed to cool slowly to a'temperature of about 640 (3., (six hfund redand forty degrees centigrade,) whereupon it is suddenly cooled, as by quenching in waterfor example, by complete immersion in water or by spraying with water or by an air-blast, but preferably in water. It is then reheated to about 600 (J. (six hundred degrees centigrade) and again suddenly cooled as before, preferably by quenching in water.

According to a modified method the firstmentioned reheating operation to about 700 C. (seven hundred degrees centigrade) followed by slow cooling is omitted, the method in other respects being like that hereinbefore described.

One or both faces of cast, nickel-chromiumsteel armor-plates treated as described can, if desired, be afterward cemented and subsequently hardened in the usual way.

It is to be understood that the invention is not limited to the employment of the particular tem peratures mentioned. as these may sometimes and with advantage-be varied to a small extent. For example, the reheating in each case may be carried to fromabout 700 .C. to 7 20 (3., (seven hundred to seven hundred'and twenty degrees centigrade.) Instead of slowly cooling to' about 640 (J. (six hundred and forty degrees centigrade) after reheating, the cooling may advantageously be .carried down only to 655 (1, (six hundred and fifty-five degrees centigrade,) and sometimes, as when dealing with large masses of steel or cemented plates, it is desirable when suddenly cooling the metal to carry such sudden cooling to a point not below, say, about 250 C. (two hundred and fifty degrees centigrade) in order to avoid any cracking of the metal. Also the final reheating may be carried to about 620 (1., (six hundred and twenty de-- grees centigrade.) 1

Steel treated in either of the ways described is found to possess excellent toughness,which renders it specially suitable for the manufac- 1 ture of armorplates, shields, and other articles, including safes or parts of safes. Satisfactory results have been obtained by treating in each of the ways hereinbefore described cast nickel-cromium steel armor-plates containing from about .3 (decimal three per cent.) to .4 %(decimal four per cent.) of car bon, about .25 (decimal two five per cent.) of manganese, about 1.8 (one decimal eight per cent.) of cromium and about 3.3 (three decimal three per cent.) of nickel, the plate being made from steel producedin the manner described in my said former specification and cast in a sand mold and having a thickness of about six inches. Such a six-inch plate attacked by common lyddite and armorpiercing projectiles of 4.7" and 6" (four decirnal seven and six inch) calibers has withstood over fifteen thousand foot tons of energy without showing a single crack. Also a fourinch plate treated as described and having a carbonized or cemented face has successfully withstood the attack of a 4.7" (four decimal seven inch) caliber armor-piercing shell. Steel treated as hereinbefore described is also capable of successfully withstanding excessive vibrating shocks, and is therefore adapted for the construction of parts of machines, also gun-carriage parts that are liable to be subjected to such shocks, and parts designed for many other purposes.

Iio

Having fully described my invention, what I claim as new, and desire to secure by Letters Patent, is

1. The herein-described process of toughenin'g steel, comprising the steps of uniformly heating the steel to a temperature up to and over 950 centigrade, and then cooling; re-

. heating the cooled steel to a temperature of from about 700 to 720 centigrade; cooling slowly to a temperature of about 640 centigrade and then quickly cooling the same; re-

heating the steel to about 600 centigrade. and finally quickly cooling the same.

' 2. The herein-described process of toughening steel, comprising the steps of uniformly heating the steel to a temperature of 950 centigrade and above, but not over 1,100 centigrade, and then cooling; reheating the cooled steel to a temperature of from 7 00 to 720 centigrade' and cooling slowly to about heating the steel to a temperature of about 700 centigrade and'cooling slowly} again raising the temperature of the steel'to about 700 centigrade and then cooling slowly to about 640 centigrade; then quickly cooling;

reheating the cooled steel to about 600 centigrade, and finally quickly cooling the same.

4. The herein-described process of toughening steel comprising the steps of uniformly heatingthe steel to a temperature up to'and oyer 950 centigrade, and then cooling; reheating the cooled steel to a temperature of from about 700 to 720. centigrade; again .quickly cooling the steel.-

raising the temperature of the steel to from 700 to 720 centigrade and cooling slowly to from 655 to 640 ceutigrade and then quickly cooling to about 250 centigrade; reheating to from 600 to 620 centigrade, and finally 5. The herein-described process of treating armor-plates of nickel chromium steel, com prising the steps of heating the plate uniforrnly up to a temperature of from about 950 to about 1,100 centigrade; and cooling slowly; reheating the cooled plate to a lower temperature, but not higher than 7 20 centigrade; cooling theplate slowly'to a temperature of from 655 tol.640 centigrade and then suddenly cooling; again reheating to a temperature not higher than about 620 centigrade, and suddenly cooling the plate.

6. The herein-described process of treating armor-plates 'of cast nickel chromium steel containing from 0.3 per cent. to 0.4 per cent.

of carbon, about 0.25 per cent. of manganese, about .8 per cent. of chromium, and about 3.3 percent. of nickel, comprising the steps of raisingthe temperature of the plate to from about 950 to about 1,100 centigrade, and cooling slowly, reheating the cooled plateto a lower temperature of about 7 00 centigrade; cooling the plate slowly to about 640 centigrade and then suddenly cooling; again reheating to a temperature of about 600 centigrade, and finally suddenly cooling the plate. In testimony whereof I have signed my name to this specification in the presence of two subscribing Witnesses. ROBERT A. HADFIELD.

Witnesses:

EUSTACE H. BURKE, LESLIE E. WHEELER. 

